jQuery.fn.center = function(d) {
	var a = this;
	if (!d) {
		a.css("margin-top", $(window).height() / 2 - this.height() / 2);
		a.css("margin-left", $(window).width() / 2 - this.width() / 2);
		$(window).resize(function() {
			a.center(!d)
		})
	} else {
		var c = $(window).height() / 2 - this.height() / 2;
		var b = $(window).width() / 2 - this.width() / 2;
		c = (c < 0) ? 0: c;
		b = (b < 0) ? 0: b;
		a.stop();
		a.animate({
			marginTop: c,
			marginLeft: b
		},
		150, "linear")
	}
};